1. Field of the Invention
The present invention relates to an image processing system and, more particularly, to an image extracting apparatus employed in an image processing system, which separates a local image corresponding to an arbitrary image area designated by a coordinate data input device, such as a graphics tablet, from an original image received through an image graphic input device, such as a scanner, a digital copier or the like.
2. Description of the Prior Art
A typical color image processing apparatus for selectively altering image color is described in U.S. Pat. No. 4,873,570 which issued on Oct. 10, 1989. The image processing apparatus has a color appointing device which enables an operator to appoint any desired color involved in an original image, a color range changing device for manually or automatically changing the size of range of the colors which can be regarded as being the same as the predetermined color, a target color appointing device for appointing a color to which the predetermined color is to be converted, and a color image forming device such as a laser beam printer for forming a color image with the predetermined color and colors in the color range converted into the target color.
Further, a digital color copier with color separation processing is disclosed in U.S. Pat. No. 5,087,968 which issued on Feb. 11, 1992. With this color separation processing employed by the digital color copier, an image reproducing copy is prepared by applying color separation to an original image of an original and processing color component signals for each of the separated colors into recording information. The color copying machine can increase the speed and efficiency of multiple copies and can provide a symmetric copy mode, a swap or inverting copy mode and a multiple image copy mode.
In such a typically conventional technique, a bit stream is defined such that a logic bit "1" is allocated to an interior of an area where coordinate data designating the extracted area is inputted from a coordinate data input device, while a logic bit "0" is allocated to an exterior of the area. Sequentially, the bit stream is logically produced with the picture image data supplied from the picture image input data to extract the desired local picture image.
However, this technique requires a separate memory having the same capacity as the amount of the picture image data supplied from the image input device to define the bit stream. As a result, a cost of embodying the memory is increased undesirably.
To overcome this drawback, a method has been proposed in which only coordinate data of the designated image area is stored in a predetermined memory and the bit stream is then defined by scanning lines when the picture image data corresponding to the designated area is input to extract the picture image of the desired image area. However, there is a problem in that the image area is partially designated with limited format.